1. Field of the Invention
The present invention relates to a method for conveying liquid metal and, more particularly, refers to a new and improved method of precise metering in pouring liquid metal as well as dosing the liquid metal.
2. Description of the Prior Art
Electromagnetic pumps and circuits for operating them are known, for instance, from European Pat. EP-No.-B1-00 43 066 which includes a description of an electromagnetic canal pump, EP-No.-A2-00 77 498 and corresponding U.S. application No. 430,543, filed Sept. 30, 1982 discloses an induction immersion pump, especially for transporting molten aluminum. A device for controlling such a pump is described in EP-No.-A2 00 95 620. In some cases, it may be desirable for technical reasons to connect two electromagnetic pumps in series, with one pump designed as an immersion pump and the other as a canal pump. In such combined pump arrangement, the immersion pump could be used, for instance, only for flooding the canal pump and then be switched off in the subsequent operation to prevent overheating. However, it has been found that for certain operating conditions, especially for the precise dosing of individual portions, that a different type of cooperation of the two pumps is needed.